Nickel base alloys containing small amounts of iron, chromium, boron and silicon are known. Such alloys are standard brazing alloys having liquidus temperatures in the range of from about 1020.degree. C. to about 1135.degree. C. These alloys generally contain up to 4% by weight of iron, up to 4.5% by weight of silicon, up to about 4% by weight of boron and up to about 16.5% chromium. Such alloys are provided under AMS specification as 4776, 4777, 4778A, and 4779. The above-mentioned nickel alloys do not have a composition similar to the materials being brazed. Some of the advantages of brazing with an alloy having a composition similar to that of the components being brazed are:
(1) There is less probability of electro-chemical corrosion in the braze area.
(2) Expansion co-efficients are well matched, reducing stesses on heating and cooling of the brazed assembly.
(3) If assembly is heat-treated, as for example in a high strength steel, properties developed by heat treatment in the braze zone are similar to those in the bulk alloy.
The above advantages are particularly effective if the brazed assembly is subjected to a diffusion heat treatment to diffuse the melting-point-lowering elements into the bulk alloy of the assembly. The greatest advantages of such alloys lies in their lower cost, which extends the range of applications where brazing is an economic alterbative to other joining processes.
Additionally, U.S. Pat. No. 3,736,128 discloses a stainless steel alloy containing 20% to 30% Cr, up to 5% Ni, up to 3% Mn, up to 2% silicon, from about 2% to 6% B. Japanese patent 148,701 discloses a steel powder containing less than 1.5% Si, less than 2.0% Mn, 0.5% to 2.0% B, 2 to 22% Ni, 10 to 25% Cr, 0.5% to 4.0% Mo, balance iron.